Optical smoke detector

ABSTRACT

An optical smoke detector comprises split optical block mounting an exciter lamp and a smoke sensing photocell in two passages directed toward an intersection zone in a dark chamber formed by one side of the block, a base with a bottom and side wall and a cover, all secured together by one screw. A light pipe from the lamp extends outside the cover to indicate lamp operation. A second photocell is in a third passage communicating with the lamp passage, the third passage mounting diffuser and pin hole apertured disks for spreading a controlled light intensity over the second photocell. The optical block assembly includes an alarm circuit board operatively connected to the photocells and physically positioning the block on the base.

United States Patent 1 1 Steele et al.

[ OPTICAL SMOKE DETECTOR [75] inventors: Donald F. Steele, Cohasset; Robert B. Enemark, Weymouth, both of Mass.

[73] Assignee: Electro Signal Lab. lnc., Rockland.

Mass.

[22] Filed: July 24, 1973 [2l] Appl. No.: 382,058

14 1 Jan. 28, 1975 I 3/l973 9/l973 Steele 356/207 X Maute 250/239 X [57] ABSTRACT An optical smoke detector comprises split optical block mounting an exciter lamp and a smoke sensing photocell in two passages directed toward an intersection zone in a dark chamber formed by one side of the block, a base with a bottom and side wall and a cover, all secured together by one screw. A light pipe from the lamp extends outside the cover to indicate lamp operation. A second photocell is in a third passage communicating with the lamp passage, the third passage mounting diffuser and pin hole apertured disks for spreading a controlled light intensity over the second photocell. The optical block assembly includes an alarm circuit board operatively connected to the photocells and physically positioning the block on the base.

17 Claims, 10 Drawing Figures OPTICAL SMOKE DETECTOR BACKGROUND OF THE INVENTION Reference is made to U.S. Pat. Nos. 3,497,303 and 3,723,747 and application Ser. No. 234,775, filed Mar. 15,1972 by Robert B. Enemark, and now U.S. Pat. No. 3,774,186.

DRAWINGS FIG. 1 is an isometric view of a fully assembled and enclosed optical smoke detector;

FIG. 2 is an exploded isometric of the detector with its face panel removed;

FIG. 3 is an enlarged, exploded isometric view of the detector with its outer cover removed;

FIG. 4 is an exploded isometric view with its inner cover removed, showing its optical block;

FIG. 5 is an isometric view of the optical block assembled;

FIG. 6 is a further enlarged, exploded isometric view of the optical block;

FIG. 7 is an enlarged horizontal section of the assembled detector view from plane 77 of FIG. 3;

FIG. 8 is a fragmentary section view from plane 8-8 of FIG. 1;

FIG. 9 is a fragmentary vertical section viewed from plane 9-9 of FIG. 1; and

FIG. 10 is bottom plan view from plane 1010 of FIG. 9 of the inner and outer covers and face plate assembled.

DESCRIPTION Generally As shown in FIGS. 1 to 4 and 7 an optical smoke detector generally comprises a molded plastic base I having a bottom wall 2 and a semicircular side wall 3, a molded plastic optical block assembly 4 including an optical block 6 and a printed circuit board 7. Over the optical block and base is a two part dark chamber cover of molded plastic including an inner cover 8 and an outer cover 9. Outside these operative parts of the detector are a molded plastic enclosing ring 11 and face plate 12.

As shown particularly in FIGS. 4 and 7 the electronic components of the detector comprise an exciter lamp 13, a smoke sensing photocell 14, a compensating photocell 16, a transformer T with alternating current input leads A, C and an alarm horn H, all connected to the printed circuit board 7.

Optical Block Assembly 4 As shown particularly in FIGS. 5, 6 and 7 the optical block is approximately symmetrically split into two mating portions 6a and 6b. Respective block portions include a bracket halves 21 receiving and holding the spring clip 22 of a holder 23 for the lamp 13. Between the lamp l3 and the inner side 24 of the block a light passage along axis Al (FIG. 7) including an annular recess for a lens 26 directing a divergent light beam along the axis Al to an opening 27 at the inner side of the block. The passage is annularly ribbed to minimize light scatter outside the beam.

The smoke sensing photocell is positioned in an annular recess 28 (semiannular in each block half) receiving the smoke sensing cell 14. From the recess 28 a second light passage 29 extends through a lens 31 along an axis A2 to a zone Z of intersection with the light beam axis Al. The smoke sensing cell views along the axis A2 through an opening 32 on the inner side of the block slightly spaced from the light beam opening 27. The two passages 27 and 29 on the respective axes A1 and A2 are preferably at a included angle.

The second, compensating photocell 16 is similarly located in an annular recess 33 at the outer end of a passage 34 extending toward a wall 36 which blocks the compensating cell from viewing outside the block. Instead the compensating cell l6 views and receives light from the lamp lens 26 passing through two diffusing disks 37 and two centrally pin-hole apertured disks 38 reducing the light reaching the compensating cell 16 to approximately the intensity of light scattered to the sensing cell 14 by smoke of density at the zone Z which will in one foot attenuate light about 2 to 10 percent.

In assembly the optical components (lamp, cells, lenses, diffusers and pin-hole disks) are laced in the annular recesses of one half of the block and the other half is mated with the first half, correct positioning being assured by two register pins 39 on half block 6b fitting in holes 41 on half block 6a. The mated half blocks may be clamped or taped together temporarily prior to being mounted as will be explained in connection with the base 1 and cover 8, 9. After mating the halves a flexible strip 42 of blackened paper is inserted in a track formed by two opposed grooves 43 above and below the inner side 24 of the block. The strip masks the photocells from ambient light allowing them to acquire operating characteristics by a period in the dark.

The mated optical block is physically joined with the printed circuit board by two screws 43 through the board into the inner side 24 of the block (FIG. 4) to complete the optical block assembly.

The circuit board carries an alarm circuit such as is shown in application Ser. No. 234,775 identified in BACKGROUND OF THE INVENTION. The lamp 13, the photocells l4 and 16, a transformer T, a horn H and suitable alternating current leads are electrically connected in the alarm circuit. The optical and electric components of the detector are then electrically operational when the masking strip 42 is withdrawn from the track 43, except that a pair of spaced terminals 45 on the circuit board must be interconnected by a temporary jumper for testing the alarm circuit, or by a spring connector described with respect to Enclosing Ring 11 and Face Plate 12.

Base 1 and Two Part Cover 8, 9

The smoke detector base 1 on which the above described optical block assembly is mounted comprises a bottom wall 2 and a circular side wall 3 extending part way around the edge of the base, specifically between two smoke ports 44 and 46. These ports are closed with panels 47 of a porous sponge-like material which, as fully described in U.S. Pat. No. 3,497,303, passes air borne smoke particles but excludes light. The side wall 3 is opposed by the optical block assembly which with the base 1 defines the bottom and sides of a dark chamber 5 around the smoke sensing zone Z.

The circuit board portion 7 of the optical block assembly comprises a planar, retangular phenolic board 7 whose parallel end edges 47 slide into two vertical slots in guides 48 upstanding from the base. So inserted in the base the inner side 24 of the optical block and one end 49 of the circuit board 7 close one side of the dark chamber between the ports 44 and 46. The board end 49 and a baffle 51 form a funnel converging toward the dark chamber and smoke sensing zone Z, tending to direct inflowing smoke toward the zone. Such directed smoke flow is aided by thermal convection through the funnel caused by the heating of one or more ohmic components 52 on the end 49 of the circuit board. This baffle 51 and other baffles 53, 54 and 56 reduce entry of ambient light into the dark chamber and scattering from the lamp beam and dark chamber walls toward the smoke cell 14.

Enclosure of the dark chamber is completed by the two part cover comprising inner cover 8 and outer cover 9. The inner cover 8 has small depending lips 57 which telescope over the side wall 3 and other upstanding portions of the base and positively position the inner cover on the base (FIG. 4). A single screw 58 whose head 59 is countersunk in a boss 61 on the inner cover 8 is selfthreaded through a hole 62 in the two halves 6a, 6b of the optical block 4 into an apertured boss 63 upstanding from the base 1 (FIG. 9). This single screw secures the inner cover, optical block and base physically in assembled condition and optically and electronically operational, except that the circuit board terminals 45 must be jumped and that an opening 64 will admit light to the dark chamber 5 and intersection zone Z. The inner cover opening may be used to admit a calibrated intensity of light to the dark chamber for testing detector operation.

The outer dark chamber cover 9, shown most clearly in FIG. 3, has a pair of register pins 66 fitting in corresponding holes 67 in the inner cover. A whorled array of curved vanes 68 blocks light from entering laterally under the outer cover to the opening 64 through the inner cover, and imparts an eddying current to smoke entering the dark chamber. Like the other register pins of the detector the pins 66 fit the holes 67 sufficiently snugly to hold the outer cover in place, with the vanes bearing on the inner cover 8 except at clearances 70, until positvely secured by the face plate 12.

Enclosing Ring 11 and Face Plate 12 The face plate 12, shown particularly in FIGS. 2 and 10, is disk shaped and with the enclosing ring 11 forms the outer decorative housing of the present smoke detector. Depending from the center of the face plate are a pair of integrally molded plastic spring detents 71 each of whose tapered free ends diverge to a shoulder 72 (FIG. 9). As shown in FIG. 10, the free ends are of different lateral width and can fit only one way through a first keyhole 73 in the outer cover 9 and a second, aligned keyhole 75 in the inner cover 8, the detent shoulders 72 then springing apart to latch inside the inner cover and positively secure the face plate 12, and outer cover 9 to the detector.

Also on the face plate is a bifurcated, conductive spring jumper connector 74 having two shouldered prongs adapted to be compressed between the two open circuit terminals 45 on the terminal board 7. These terminals may be in one of the alternating current supply leads to the alarm circuit, that is forming an interruption in that lead closed by the jumper 74. If the open circuit terminals carry high voltage they should be recessed in an insulating shroud 76 beyond manual contact.

The face plate has a circular opening 77 for receiving the outer end of a tinted translucent light pipe 78 flush with the outside of the face plate. The light pipe is held frictionally in a socket 79 (FIG. 5) in one optical half block 6a (FIG. 6), which socket opens inwardly to the lamp 13. The pipe 78 extends from the optical block through snug holes 81 and 82 in the inner and outer covers respectively and indicates burning of the lamp 13.

The face plate may be snap fitted on the detector either before or after the decorative enclosing ring is secured by the bayonet attachment of studs 83 on the base 1 in grooves 84 inside the ring.

With the detector fully assembled smoke has access to the dark chamber 5 through the ports 44 and 46 and the inner cover opening 64. These ports enter the dark chamber at three widely divergent solid angles. that is not only laterally from opposite sides of the smoke detector but also through the inner cover opening at right angles to the plane of the lateral angles. This wide solid angle approach, the thermal convection and the whorled vanes of the outer cover greatly aid the flow of smoke in at least one path through the three openings regardless of the orientation of the detector on a wall or a ceiling, or the external flow of smoke.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

We claim:

1. An optical smoke detector structure comprising:

a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light excluding and smoke transmissive entry to the dark chamber, an optical block assembly forming means to position an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block, the block comprising means to shield the photocell from direct light from the lamp, guide means on the base slidingly receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define a dark chamber, and

a light excluding cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and operational assembly of the smoke detector, the cover and sidewall having integral telescopingly interengaging portions positively positioning the cover on the base.

2. A detector according to claim 1 wherein a lamp and photocell respectively are mounted in said support means, the lamp emitting a light beam into the dark chamber and the cell sensing light scattered by smoke from the beam.

3. A detector according to claim 1 wherein a lamp and photocell are mounted in said respective support means of the block, and the block comprising an open ended socket adjacent to the lamp and a light pipe held in the socket, and an aperture in the cover aligned with the socket through which the light pipe extends to the exterior of the cover to indicate operation of the lamp.

4. A detector according to claim 1 wherein the cover comprises two mating parts, an inner cover fitting the optical block and having an aperture opening into the dark chamber, and an outer cover fitting over the aperture and including means passing smoke and excluding light from the aperture.

5. A detector according to claim 4 wherein the base side wall comprises a porous material excluding light and passing smoke and cooperating with the cover aperture to circulate amoke through the dark chamber in various installed orientations of the detector.

6. A detector according to claim 2 wherein the optical block assembly comprises a planar circuit board mounting the electronic components of an alarm circuit, the board having parallel edges at opposite ends, and the guide means on the base comprising grooved means receiving the parallel edges.

7. A detector according to claim 6 wherein the cover engages the board to secure it in place.

8. A detector according to claim 6 wherein the optical block and circuit board are physically joined, and a lamp and photocell are mounted in the support means of the base and are electrically, operationally connected to the alarm circuit and responsive to sensing of smoke by the cell to indicate a predetermined smoke density.

9. A detector according to claim 1 wherein said cover comprises a keyhole shaped aperture and the optical block assembly includes a pair of spaced electrical terminals, the detector further comprising a face plate overlying the cover, the face plate having a key snapfitting in the keyhole and a spring detent snapfitting between the terminals electrically to connect the terminals and secure the face plate to the detector.

10. A detector according to claim 9 wherein the detector includes an electronic alarm circuit operatively connected through said terminals and detent.

11. A smoke detector according to claim 1 wherein the base sidewalls and cover form smoke passages communicating with the dark chamber on at least three substantially divergent solid angles.

12. An optical smoke detector structure comprising:

a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light excluding and smoke transmissive entry to the dark chamber,

an optical block assembly forming means to support an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block, the optical block comprising two substantially symmetrical mating halves with semi-annular recesses receiving the photocell and forming the passages and spaced openings,

means on the base receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define the dark chamber, and

a cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and assembly of the smoke detector.

13. A detector according to claim 12 wherein the optical block includes a second photocell with a photosensitive surface the block forming a third passage therefrom to the lamp passage, and the third passage mounting at least one diffuser disk and at least one pin hole apertured disk aligned with the second cell to diffuse a controlled amount oflight over its photosensitive surface.

14. An optical smoke detector structure comprising: a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light exclusing and smoke transmissive entry to the dark chamber, an optical block assembly forming means to support an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block,

means on the base receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define the dark chamber, and

a cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and operational assembly of the smoke detector,

wherein said one side of the optical block comprises a track slidingly receiving a flexible strip over the cell opening thereby to mask the cell, the base side wall having an outlet therethrough adjacent to one end of the track, and a flexible strip in said track including means extending through said outlet, whereby the detector may be assembled while maintaining the cell in the dark, whereafter the strip may be withdrawn from the track unmasking the cell for operational sensing of light in the dark chamber.

15. An optical smoke detector structure comprising:

a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light excluding and smoke transmissive entry to the dark chamber,

an optical block assembly forning means to support an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block,

means on the base receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define the dark chamber, and

a cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and operatonal assembly of the smoke detector,

wherein the optical block assembly comprises a planar circuit board mounting the electronic components of an alarm circuit, a portion of the board forming with the base side wall a passage to the dark chamber, the circuit including an ohmic component heating air in the passage to promote smoke circulation.

16. A detector according to claim 15 wherein said circuit board portion and the side wall converge in a funnel toward the dark chamber.

17. A detector according to claim 16 wherein the lamp and cell passages are aligned with an intersection zone and the funnel converges toward the zone. 

1. An optical smoke detector structure comprising: a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light excluding and smoke transmissive entry to the dark chamber, an optical block assembly forming means to position an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block, the block comprising means to shield the photocell from direct light from the lamp, guide means on the base slidingly receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define a dark chamber, and a light excluding cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and operational assembly of the smoke detector, the cover and sidewall having integral telescopingly interengaging portions positively positioning the cover on the base.
 2. A detector according to claim 1 wherein a lamp and photocell respectively are mounted in said support means, the lamp emitting a light beam into the dark chamber and the cell sensing light scattered by smoke from the beam.
 3. A detector according to claim 1 wherein a lamp and photocell are mounted in said respective support means of the block, and the block comprising an open ended socket adjacent to the lamp and a light pipe held in the socket, and an aperture in the cover aligned with the socket through which the light pipe extends to the exterior of the cover to indicate operation of the lamp.
 4. A detector according to claim 1 wherein the cover comprises two mating parts, an inner cover fitting the optical block and having an aperture opening into the dark chamber, and an outer cover fitting over the aperture and including means passing smoke and excluding light from the aperture.
 5. A detector according to claim 4 wherein the base side wall comprises a porous material excluding light and passing smoke and cooperating with the cover aperture to circulate amoke through the dark chamber in various installed orientations of the detector.
 6. A detector according to claim 2 wherein the optical block assembly comprises a planar circuit board mounting the electronic components of an alarm circuit, the board having parallel edges at opposite ends, and the guide means on the base comprising grooved means receiving the parallel edges.
 7. A detector according to claim 6 wherein the cover engages the board to secure it in place.
 8. A detector according to claim 6 wherein the optical block and circuit board are physically joined, and a lamp and photocell are mounted in the support means of the base and are electrically, operationally connected to the alarm circuit and responsive to sensing of smoke by the cell to indicate a predetermined smoke density.
 9. A detector according to claim 1 wherein said cover comprises a keyhole shaped aperture and the optical block assembly includes a pair of spaced electrical terminals, the detector further comprising a face plate overlying the cover, the face plate having a key snapfitting in the keyhole and a spring detent snapfitting between the terminals electrically to connect the terminals and secure the face plate to the detector.
 10. A detector according to claim 9 wherein the detector iNcludes an electronic alarm circuit operatively connected through said terminals and detent.
 11. A smoke detector according to claim 1 wherein the base sidewalls and cover form smoke passages communicating with the dark chamber on at least three substantially divergent solid angles.
 12. An optical smoke detector structure comprising: a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light excluding and smoke transmissive entry to the dark chamber, an optical block assembly forming means to support an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block, the optical block comprising two substantially symmetrical mating halves with semi-annular recesses receiving the photocell and forming the passages and spaced openings, means on the base receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define the dark chamber, and a cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and assembly of the smoke detector.
 13. A detector according to claim 12 wherein the optical block includes a second photocell with a photosensitive surface the block forming a third passage therefrom to the lamp passage, and the third passage mounting at least one diffuser disk and at least one pin hole apertured disk aligned with the second cell to diffuse a controlled amount of light over its photosensitive surface.
 14. An optical smoke detector structure comprising: a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light exclusing and smoke transmissive entry to the dark chamber, an optical block assembly forming means to support an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block, means on the base receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define the dark chamber, and a cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and operational assembly of the smoke detector, wherein said one side of the optical block comprises a track slidingly receiving a flexible strip over the cell opening thereby to mask the cell, the base side wall having an outlet therethrough adjacent to one end of the track, and a flexible strip in said track including means extending through said outlet, whereby the detector may be assembled while maintaining the cell in the dark, whereafter the strip may be withdrawn from the track unmasking the cell for operational sensing of light in the dark chamber.
 15. An optical smoke detector structure comprising: a base forming a bottom wall and a side wall partially surrounding a dark chamber and having a light excluding and smoke transmissive entry to the dark chamber, an optical block assembly forning means to support an exciter lamp and a photocell and passages respectively leading from the lamp and cell to spaced openings at one side of the block, means on the base receiving the optical block assembly and positioning said side of the block opposite the base side wall thereby to define the dark chamber, and a cover for the dark chamber fitting over the block and side wall to complete enclosure of the dark chamber and operatonal assembly of the smoke detector, wherein the optical block assembly comprises a planar circuit board mounting the electronic components of an alarm circuit, a portion of the board forming with the base side wall a passage to the dark chamber, the circuit including an ohmic component heating air in the passage to promote smoke circulation.
 16. A detector according to claim 15 wherein said circuit board portion and the side wall converge in a funnel toward the dark chamber.
 17. A detector according to claim 16 wherein the lamp and cell passages are aligned with an intersection zone and the funnel converges toward the zone. 